Hi Dilyan,
At 10:22 17-07-2007, Dilyan Palauzov wrote:
Let's limit us now on hosts, that do not offer PRDR.
** 550 Mail for mailing-list(_at_)example(_dot_)org rejected **
> The 550 code means that mail to the above-mentioned recipients
(spamtrap(_at_)example(_dot_)org and
> mailing-list(_at_)example(_dot_)org was rejected for policy reasons. A DSN
may be sent by server.example.com
> to both recipients. The recipients may not see your reject
message or they may not understand it.
Is there any software nowadays, that sends DSN to the recipients
telling them that they cannot receive emails?
Some MTAs still send DSNs to the recipients to inform them that their
email could not be delivered. For example, if this email is not
accepted by the mail server that operates this mailing list, I will
get a DSN from my mail server.
Quoting Section 6.1 of RFC 2821:
"When the receiver-SMTP accepts a piece of mail (by sending a "250 OK"
message in response to DATA), it is accepting responsibility for
delivering or relaying the message. It must take this responsibility
seriously."
In my eyes, for normal users when a server answers with "550 Mail
rejected", the sending user receives a mail, telling her "The server
said: 550 Mail for mailing-list(_at_)example(_dot_)org rejected". What does the
user think now? Does she come to the idea, despite what is written
in RFC 2821, that the mail has reached no of the other recipients or
she is unable to understand this non-standard message, while having
no problems with interpreting standard responses?
The normal user may see the mail (DSN) as incomprehensible. There is
no guarantee that the reject message will be relayed to the sending
user. People actually expect email to work (mail delivered to
intended recipient). The expectations wans as they gain first hand
experience of the side-effects of antispam measures.
The problem is with mailing list software, which will be unable to
automatically unsubscribe faulty addresses. LSoft has solved it in
listserv using 'passive probing" (see the second half titled
"passive probes" in
http://www.lsoft.com/news/techtipLSV-issue1-2006-us.asp ). The
mailing lists are therefore not such a big problem. Imagine all
mails for me(_at_)forward(_dot_)example(_dot_)int are redirected to me(_at_)example(_dot_)com .
Already now when me(_at_)forward(_dot_)example(_dot_)int is subscribed to one mailing
list, and the mailbox me(_at_)example(_dot_)com disappears traceless, the mail
server gets the message, that mails for me(_at_)example(_dot_)com cannot be
delivered. But me(_at_)example(_dot_)com is not subscribed to the list. So now
what? (more detailed at
http://mail.aegee.org/lists/listowners-life.html#suspicious-subscribers
). It is the same as receiving "550 Mail for
mailing-list(_at_)example(_dot_)org rejected".
You can use VERP and track down which subscription is bouncing with it.
Is it possible to include in 2821bis, that software implementing it
has to support the PRDR extension? This will be additional
motivation for all programmers to implement it.
That falls outside the scope of RFC 2821bis.
2821bis compliant sounds much better than PRDR compliant and I
suppose the programmers shall want to be 2821bis compliant.
PRDR may have better traction that other extensions from sites
running mail filters as they benefit from it.
Let me rephrase my previous question:
Does anybody see any _negative_concequences_ (was disadvantages) of
ending the session
EHLO server.example.com
250 OK server.example.org
MAIL FROM:<spammer(_at_)example(_dot_)com>
250 OK
RCPT TO:<spamtrap(_at_)example(_dot_)org>
250 OK
RCPT TO:<mailing-list(_at_)example(_dot_)org>
250 OK
DATA
354 OK
That is all.
.
with
550 Mail rejected by mailing-list(_at_)example(_dot_)org
which _de_facto_ implies, that the mail was accepted by all but
mailing-list(_at_)example(_dot_)org?
Yes, I see several:
1. That reply code applies to all recipients of the message.
2. I don't understand English
3. My MTA does not convey the actual reject message to me.
4. My MTA silently drops DSNs.
Regards,
-sm